Waste-to-energy valorization of rubber seed shells into carbonized briquettes using a novel heat-enhanced food waste binder

Commercial starch binders increase production costs and compete for food resources; hence, there is an urgent need to investigate sustainable alternatives in biomass briquetting. This study demonstrates that thermal modification of food waste into a high-performance binder for rubber seed shells (RSS) carbonized briquettes is possible. Systematic investigations into boiling time (0-30 min) and binder loading (30-50%) demonstrated that heat treatment significantly improved compressive strength from 0.307 to 0.508 MPa, or by 65%. Field emission scanning electron microscopy (FE-SEM) analysis confirmed better matrix cohesion and dispersibility of binder in thermally treated samples. Higher binder content, though effective in improving densification, reduced fixed carbon and consequently higher heating value (HHV) due to increased volatile fractions. The best-performing formulation containing 40 wt.% binder and 20-min boiling showed excellent performance with a bulk density of 715 ± 21 kg/m³, volatile matter of 50.84 ± 3.03%, fixed carbon of 41.07 ± 3.42%, HHV of 5,060 ± 112 cal/g, burning rate of 0.875 ± 0.016 g/min, and compressive strength of 0.625 ± 0.029 MPa. These results demonstrate that simple thermal activation can significantly improve the binding performance of food waste, supporting its practical application as a sustainable binder for RSS carbonized briquettes while further valorizing organic waste streams. This approach provides a promising pathway for converting two underutilized waste streams into a value-added solid biofuel.